[Python-ideas] set.add() return value
Bill Janssen
janssen at parc.com
Mon Feb 16 20:47:07 CET 2009
Steven D'Aprano <steve at pearwood.info> wrote:
> Greg Ewing wrote:
> > Chris Rebert wrote:
> >
> >> As The Zen says: "Special cases aren't special enough to break the
> >> rules."
> >
> > What might be more acceptable is to add a new method
> > for this, with a name suggesting that it's more than
> > just a plain mutating operation, e.g.
> >
> > was_it_there = myset.test_and_add(42)
> >
>
> What's the use-case for this? What's wrong with doing this?
>
> if 42 in myset:
> myset.add(42)
Well, for me, What's wrong is that it's complex to write and debug,
mainly. Don't you mean to say,
was_it_there = (42 in myset)
if not was_it_there:
myset.add(42)
for instance? Not that I'm pushing for the addition of this method, but
I see the point.
Bill
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